Potentiometer



July 27, 1965 w.l D. HULBERT 3,197,727

POTENTIOMETER Original Filed Sept. 12, 1962 3 Sheets-Sheet 1 ffm MM July 27, 1965 w. D. HULBERT POTENTIOMETER 3 Sheets-Sheet 2 origina Filed sept. 12. 1962 July 27, 1965 w. D. HULBERT 3,197,727

POTENTIQMETER Original Filed Sept. 12, 1962 3 Sheets-Sheet 3 #Trax/uffi:

United States Patent O 3,197,727 FOTEN'HMETEER Warren D. Hulbert, Hacienda Heights, Caiif., assigner to Speetrol iiiectronies Corporation, San Gabriel, Calif., a corporation oi' Deiaware Original appiication Sept. 12, 1962, Ser. No. 223,229. Divided and this application Feb. 1, 1965, Ser. No. 429,462

13 Claims. (Ci. 338 175) This invention relates to variable resistors, and more particularly to potentiometers which may be constructed in an exceedingly small size.

The present application is a divisional application of my copending application Serial Number 223,229, tiled September 12, 1962, which was a continuation-in-part application of my earlier application Serial Number 51,879, tiled August 25, 1960, and now abandoned.

The requirement for variable resistors of the potentiometer type to permit line adjustment of electrical resistance in electronic and electrical circuits has long been recognized in the prior art and such potentiometers of various sizes and shapes have been developed for this purpose. For example, the rectilinear potentiometer, the lead screw actuated potentiometer and the worm screw and gear actuated potentiometer are known to the prior alt. While these prior art potentiometers have been quite successful for the purposes for Which they were developed, the various sizes and shapes necessitated by the particular inner mechanisms of each of the different types of potentiometer have caused them to be physically non-compatible with other circuit components such as, for example, transistors, resistors, diodes and the like. Furthermore, as a result of these physical limitations, the prior art potentiometers have not been readily adaptable for use in microcircuit applications such as printed circuits.

For the most part, the prior art potentiometers of the types above referred to have required relatively complex interior mechanisms to provide the operation which is required in the electrical and electronic circuits which utilize such potentiometers. As a result thereof, the size of these potentiometers has been greater than desired in some applications and they have not included designs permitting them to be incorporated along with other circuit components and subsequently encapsulated in plastic or other potting compounds to form a complete sealed module for use in computers and the like.

Accordingly, it is an object of the present invention to provide a potentiometer having an exceedingly small size, that is, subminiature, and which is very light in weight and which is mechanicaliy simple, rugged, and inexpensive to manufacture.

lt is another object of the present invention to provide a potentiometer which is compatible both as to size and configuration with small size electrical components.

it is another object of the present invention to provide a potentiometer which is readily adaptable for use in printed circuits.

it is another object of the present invention to provide a potentiometer which is housed in such a manner that it may be encased in plastic or other potting compounds along with additional electrical components comprising an electrical or electronic module.

Additional objects and advantages of the present invention will become apparent from a consideration of the following description taken in conjunction with the accompanying drawings in which similar parts are designated by the same reference numeral and which are presented by way of example only and are not intended as a limitation upon the scope of the present invention and in which:

ICC

FIG. 1 is a perspective View of a potentiometer in accordance with the present invention;

FiG. 2 is a cross-sectional view of the potentiometer of FIG. 1 taken about the lines 2 2;

FIG. 3 is a cross-sectional view oi the potentiometer of FIG. 2 taken about the lines 3 3;

FIG. 4 is a cross-sectional view of an alternative embodiment of a potentiometer in accordance with the present invention;

FIG. 5 is a partial view of the structure of FIG. 4 taken about the lines 5 5 thereof;

FIG. 6 is an axial cross-sectional view of another al ternative embodiment of a potentiometer in accordance with the present invention;

FIG. 7 is a partial view of the structure of FIG. 6 taken about the lines 7 7 thereof;

FIG. 8 is a partial, axial cross-sectional view of an alternative embodiment of a portion of a potentiometer in accordance with the present invention;

FIG. 9 is a partial, axial cross-sectional view of a portion of a potentiometer in accordance with the present invention.

In accordance with one aspect of the present invention, there is provided a potentiometer having a housing which includes a casing and a base and which deiines an internal cavity. A resistance element is positioned within the cavity and fixed electrical connection is made to the resistance element. An electrically conductive element is positioned internally of the housing and is electrically attached to means extending through the base to provide an external electrical connection. A bearing surface is also provided internally of the housing. A rotor having a wiper arm affixed thereto which makes slidable contact with the resistance element is positioned substantially at the center of the housing and includes bearing means which engages the bearing surface. The wiper arm and the electrically conductive element are electricaily interconnected to provide an external electncal connection to the resistance element.

In accordance with a more specific aspect of the present invention, the bearing surface and the electrically conductive element above referred to comprise an electrical lead which is semi-rigid and which extends through the base of the housing and into the interior thereof. The rotor includes a member of electrically non-conductive material having an axial opening. The axial opening receives the portion of the electrical lead internal of the housing in such a manner that the rotor is rotatably supported upon the lead substantially at the center of the cavity. The rotor also includes a slotted opening transverse to the longitudinal axis thereof and communicating with the axial opening above referred to. One end of the wiper arm is inserted through the slotted opening and receives the electrical lead in such a manner that the wiper arm is locked in place mechanically between the electrical lead and the axial opening in the rotor and good electrical contact is provided thereby.

Referring now to the drawings, and more particularly to FIG. 1, there is illustrated a potentiometer in accordance with the present invention. As is therein shown, the potentiometer iti includes a housing having a casing 11 and a base 12. Protruding through and extending from the base 12 are electrical connections 13, 14 and 15 which preferably are electrically conductive leads which are rigid or semi-rigid in nature and which may be plugged into a proper socket membe-r lsuch as, for example, a transistor grid. These leads may be cemented, for example with an epoxy res-in, at the base 12 to provide a dust and moisture proof seal for the housing. A slotted head :te protrudes from the top of the casing 11 and may be utilized to vary the resistance of the potentiometer as will be explained more fully hereinafter.

Reterring now more particularly to FlGS. 2 and 3, the internal construction of a presently preferred embodiment of the potentiometer itl Iis illustrated. As is illustrated, the housing delines a substantially circular internal cavity il?. The hase l2 is preferably a molded plastic material such as a phenolic resin and has an annular ring 13 extendint7 upwardly therefrom. The outer surface of the annular ring ftd mates with the inner surface of the casing l1 and the juncture therebetween is cemented t0 provide a dust and moisture proof seal for the potentiometer. The annular ring it; is reduced in thickness at its upper portion to form an internal ledge i9 upon which a resistance element 2@ is supported.

The resistance element Ztl is illustrated as a circular mandrel having resistance wire wound thereahout in a conventional manner. it should, however, be expressly understood that the esistance element Ztl may be of any type known to the art such as, for example, a wire would card, a lm or layer of resistive material deposited upon a base therefor in accordance with well-known techniques or the like.

Electrical connection is provided to one end of the resistance element Ztl by way or a connective lead 21 which is soldered, welded or otherwise electrically connected to the lead l5 extending through the base l2. A similar electrical connection is provided to the opposite end of the resistance element Ztl by connective lead Zlcz which is atlixed to electrical lead ld.

Leads i4 and l5 extend through the base l?, and are bent so as to fit within recesses la and a respectively. Such construction provides a greater surface to which the connective leads 2l and 2te may be attached to thereby facilitate assembly of the potentiometer. Such construction also provides a more rigid anchor for the leads. lt should also be noted that lead i3 is bent intermediate its end points to provide a substantially horizontal portion which also ts within a recess 13a in the base l2. As before, such construction provides greater rigidity for the lead 1 3 and the purpose therefore will become more apparent in the following description. The two ends of the lead 13 extend through the base l2 so that one end thereof extends externally of the housing and the other end extends internally of the housing .and into the cavity 17.

That portion of the lead i3 which extends internally of the cavity 17 is positioned substantially at the center of the base l2. The lead i3, as well as the leads ld and l5, are molded in place in the base member l2. Preferably, however, these leads are pressed into place through openings which are provided therefor at the time the base 12 is molded. ln eit-her case, in the presently preferred embodiment of the present invention the lead t3 is preterably held stationary and provides a bearing surface for the rotor 22 which is mounted thereon. Rotor 22 is preferably an electrically non-conductive material such as Teflon, Kel F, a ceramic or the like. rthe rotor 22 is provided with a substantially axial opening longitudinally thereof and which extends through only a portion of its length. This lopening receives the internally extending portion of lead is thus providing a post upon which the rotor rotates. A slotted opening 23 is provided through the rotor 22 transverse to the longitudinal axis and communicates with the axial opening which receives the interna-l extending port-ion of the lead i3. The slotted opening 23 receives one end Ztl of the wiper arm 2S which has the opposite end 26 in slidable electrical contact with the surface of the resistance element 2li. A depression 2'7 is provided in the end 2d of the wiper arm 25 in order to provide mechanical strength and to better support the wiper arm Z5 within the slotted opening 23 of the rotor 22. The wiper arm is preferably constructed of precious metal, such as a platinum alloy, or the electrical equivalent thereof, and is stamped from a plate or sheet of the material as one continuous member having the depression 27 and contact 26.

' provided by the axial opening in the rotor 22.

e las :for

A rotor head Ztl includes a lange 3l having a recess 32, therein. Within the recess 32 there is disposed a washer or (lt-ring 33, which is preferably constructed of silicone rubber, and which provides .a dust and moisture proof seal between casing llt and the internal cavity 17 of the housing. A recess 3d is provided within the rotor head Ztl for receiving the upper portion of the rotor 22 in a press tit or by insert molding or the like. Although the rotor head 2S is illustrated as a metallic substance such as stainless steel, it is to be expressly understood that it may he an electrically non-conducting material such as nylon or the like and the rotor 22 and rotor head 2S may he constructed as one integral unit.

In assembling the potentiometer asillustrated in FIGS. 2 and 3, the resistance element Ztl is placed upon the ledge 19 of the base l2 having leads therein and the con nective leads 2l and 2l@ are attached to the leads l5 and ld respectively. The wiper arm 25 is inserted into the slotted opening 23; and the rotor Z2 with the wiper arm thus contained is pressed over the internally extending portion of the lead t3. As the rotor is pressed over the lead i3, the lead contacts the end 2d of the wiper arm 2S and forces it into the position as illustrated in FIG. 3. That is, the end 2d or the wiper arm 25 is caused to become depressed and to conform to the surface of the recess provided by the longitudinal axial opening through the rotor 22. In this manner, firm, mechanical locking for the wiper arm 25 is provided between the surfaces of the lead ll?? and the longitudinal axial opening through the rotor 22. At the same time, positive electrical connection is also provided between the wiper arm 25 and the lead 13. Alternatively, the end 24 of the wiper arm 25 may have a slight depression formed therein during its manufacture. This depression then fits into the recess In any event the wiper arm is arranged so that positive mechanical locking is eitected between the lead i3 and the rotor Z2 and good electrical connection is provided. After the rotor 22 is pressed into place, it may be positioned so that the wiper arm slidably contacts the resistance element Ztl at the desired position. The O-ring is then dropped in place and the casing l1 is pressed over the annular ring 18 and cemented to provide a dust and moisture proof sealed housing.

lt should be noted that the O-ring 33 and the mating surfaces between the casing lll and the annular ring ll provide a housing which is sealed against the entry of moisture, dust, or other foreign matter. This sealed housing permits a potentiometer in accordance with the present invention to be completely immersed in a potting compound without fear of leakage. All known prior art devices are subject to such leakage and as a result thereof Y attempts at potting have been unsuccessful.

If desired, the interior cavity of the potentiometer may be atleast partially ltered with a viscous liquid such as silicone grease. The presence of such a liquid aids in damping any vibrations which may occur in the wiper arm contact with the resistance element if the potentiometer is subjected to severe stress. The liquid also suspends any wear products that may be generated by use of the potentiometer and thereby prevents them from possibly interfering with the operation of the potentiometer. In addition to the foregoing, the silicone grease provides an excellent lubricant and heat sink which improves the operation and characteristics of the potentiometer.

If such is desired, a potentiometer in accordance with the present invention may include a stop mechanism which, for example, may be an extension 35 of the molded base l2 which extends upwardly from the annular ring 18 so that a projection 3o from the rotor head 2S will Contact it at the desired point thereby preventing the wiper arm from rotating past a desired point on the resistance element. The stop mechanism may also include other means well known to the art, such as an inward anew/a7' il indentation in the casing ll and an eccentric rotor head or the like.

The illustrations of the presently preferred embodiment of a potentiometer in accordance with the present invention are greatly exaggerated in size for clarity of illustration and ease or" description. A typical potentiometer in accordance with the present invention is no larger in size than the standard transistor, and for example, may have, exclusive of the internally extending portions of the electrical leads, a diameter of .345 inch and a height of .276 inch and a weight of approximately l gram. Because of these magnitudes of geometric dimensions, such embodiments of the invention are typically designated as subminiature Utilizing a housing of the above dimensions and a structure such as that above described and shown in the drawings, the potentiometer may have a total resistance of 50,000 ohms and may dissipate 1 watt at 70 C. ambient.

Although in presently preferred embodiments of the invention above described the base member for the housing is constructed of an electrically non-conductive material, it should be expressly understood that in those instances where it is desired to dissipate larger amounts of power the base may be construced of a material having better heat conduction such as aluminum. When such material is utilized for the base, a very thin insulative material is disposed between the resistance element and the base. An example of such material may be anodized aluminum or the like. Each of the electrical leads extending through the base member are then surrounded by an insulating material which is bonded to the metallic base in accordance with well known techniques as to provide a seal between the lead and the base and yet maintain the base insulated from the electrical connections. By using a base of the type above described, the potentiometer may dissipate 2 watts at 70 C. ambient.

Referring now more particularly to FIGS. 4 and 5 there is illustrated an alternative embodiment of a potentiometer in accordance with the present invention. As is therein shown there is provided a housing having a casing ill and a base 42. A resistance element i3 is seated upon a ledge 44 which is molded into the base i2 similar to that above described. It should be noted that the resistant element 43 is constructed of an elliptical mandrel or card upon which there is wound a resistance wire in accordance with Well known techniques. Appropriate electrical connection is made to the resistance element t3 by way of a connective lead 45 and is carried externally of the housing by lead 416. Similar external electrical connection is provided to the 'opposite end of resistance element 43. An electrically non-conductive rotor 22' having a rotor head 47 which is sealed by way or an O-ring 33 is positioned substantially at the center of the housing upon a spindle 48. The spindle 48 lits within an axial opening in the rotor 22 and mechanically locks the wiper arm 49 into appropriate position to contact the resistance element 43.

It should be noted that rotor 22 does not extend to the top surface of the base 42 but instead is spaced therefrom. The spindle 48 protrudes a short distance from the rotor 22 and seats into a bearing surface 5?. at the center of the base. In this manner the spindle @t3 positions and supports the rotor 22 so thatit is rotatably positioned substantially at the center of the potentiometer. As the rotor is manually rotated the wiper arm slides upon the surface of the resistance element 43. It should be noted that the rotor head 47 is constructed of an electrically non-conductive material.

External electrical connection is provided to the wiper arm in the presently preferred alternative embodiment, by providing a second arm 52 extending downwardly to slidably engage an electrically conductive collector bar 53 positioned concentrically with the rotor 22 upon the base 42. The collector bar 53 electrically contacts lead Se to provide the external electrical connection. The remaining portions of the potentiometer are similar in construction and operation to that above described.

Referring now more particularly to FlGS. 6 and 7, there is illustrated another alternative embodiment of a potentiometer in accordance with the present invention. As is indicated by the use of the same reference numerals the potentiometer includes, for the most part, structure similar to that of FlGS. 4 and 5. However, particular attention is directed to the manner in which external electrical connections are made to the wiper arm. This external electrical connection is provided by a lead S5 having a cup-shaped bearing surface Se which receives an extension 57 of the rotor 5S. As is illustrated in FIG. 6, rotor 53 is preferably a metallic electrically conductive member. The rotor head 47 is therefore an electrically non-conductive material such as Teilon or the like to insulate the wiper arm from the casing 41. The construction of the rotor head is similar to that above described with respect to FiGS. 2 and 3, and includes provision for an O-ring 33 in order to provide a dust and moisture proof seal. A wiper arm 59 is aliixed to the rotor 58 in order to provide slidable electrical contact with the resistance element As is illustrated more clearly in PEG. 7, the wiper arm 59 is axed to the rotor 58 by spotwelding, soldering or the like. lt is therefore seen that in accordance with this embodiment of a potentiometer in accordance with the present invention, electrical contact to the resistance element is provided by way of the wiper arm 59, the electrical conductor which comprises the rotor 5S and through the bearing surface Se and the extension 57 of the rotor 52% to the external lead 55.

The rotor mechanism in accordance with the present invention may also be constructed in additional alternative forms. For example, as is illustrated in FIG. 8, the rotor may include a non-conductive member dlt having an axial opening adapted to receive a pin member 62 therethrough. The wiper arm 63 is inserted Within a transverse slotted opening which communicates with the axial opening in the rotor 6l and is mechanically locked in place in a manner similar to that above described in connection with FIGS. 2 and 3. The base 64 of the housing has molded as a part thereof an external electrical connection 65 having an inner surface 66. The inner surface do provides a `bearing surface 67 into which the pin member 62 is seated in bearing engagement to rovide support for the rotor 6l. The rotor el supports the wiper arm 63 which provides electrical connection to the resistance element (not shown) which is mounted within the housing.

FIG. 9 illustrates another alternative embodiment of the rotor mechanism, and as therein illustrated, includes a rotor 7i constructed of a non-metallic insulating type iaterial having a cap or sleeve 7?; about the outer surface thereof. A wiper arm 73 is welded, soldered or otherwise mechanically and electrically connected to the sleeve The sleeve 72 also includes a projection 70 extending therefrom. The base 74 has molded therein an external electrical connection 75 having an inner surface 76 which provides a bearing surface similar to that described in conjunction with FIG. 6. Electrical connection of the rotor construction to the resistance element is provided by way of wiper arm 73, cap 72 and tane extension thereof 7@ to the external electrical lead f5. The bearing surface 7o provides mechanical support for the rotor mechanism Tl as well as electrical connection.

From the foregoing description of the various embodiments of the potentiometer in accordance with the present invention, it is seen that in each case there is provided a substantially centrally located rotor mechanism which carries a wiper arm which provides a slidable electrical connection to the resistance element. Electrical connection is then provided between the wiper arm and an elecaaai/,var

trical lead extending through the housing'prcferably the base number, to provid-c an external electrical connection. it should be noted that in each case the rotor is a mechanically simple and preferably unitary member which permits construction 4of an excccdinG-ly smal-l or subminiature potentiometer. lt is also seen that in cach case the rotor head and rotor body are constructed ot materials in such a manner that the wiper arm is electrically insulated from the casing of the housing.

There has thus been disclosed a potentiometer which is capable of being constructed in exceedingly small, is, subminiature size and which is simple, rugged, inexpensive to manufacture and is compatible with other modern electronic: and electrical components, and is adaptable for utilization in printed circuits.

What is claimed is:

l. A potentiometer comprising: a housing including an electrically non-conductive base member having rist, second and third electrically cond ctive leads spaced apart and extending therethrough, 'sa t base member having an annular portion extend -g upwardly theretrom and defining a ledge intermediate the ends thereof, a resistance element seated upon said ledge, electrical connections between the ends of said resistance elci said tirst and second electrical leads, said third electrical lead including a pin member extending upa ardly into interior of said housing, an electrically non-conductive rotor having an axial opening xtending at least partially therethrough, said axial opening receiving said pin member to thereby rotatably support said rotor, a slotted opening transverse of said axial opening and communicating therewith, a wiper arm in slid-able engn gement with said resistance clement and extending throug said slotted opening, said wiper arm being disposed between pin member and said rotor member to thereby retain said Wiper arm in place with respect to said rotor and to provide electrical connection to said resistance element, and a head upon said rotor, said head including a recess acapted to receive an O-ring seal and a slotted extension protruding from said housing to thereby permit manual adjustment of said wiper arm upon said resistance element.

2. A potentiometer comprising: a housing having enclosing walls deiining an internal cavity, a resistance clement positioned about the periphery of said cavity, a pair of fixed electrical connections to said resistance element and extending through said housing, an electrically conductive element extending externally of said housing, a bearing surface internally of said housing and positioned substantially at the center thereof, a rotor positioned substantially at the center of said housing and upon said bearing surface, a wiper arm ai'iixed to said rotor and having slidable engagement with said resistance element, and means electrically interconnecting said wiper arm and said electrically conductive element to provide external connection to a movable point on said resistance element intermediate said pair of ixed electrical connections, said bearing surface and said electrically conductive element being secured to said housing and forming therewith substantially sealed portions of said enclosing walls, said bearing surface including a cup-shaped member and said rotor including an electrically conductive elernent extending therefrom into engagement with said cup-shaped member.

3. A potentiometer comprising: a housing having enclosing walls deiining an internal cavity, a resistance element positioned about the periphery of said cavity, a pair of fixed electrical connections to said resistance element and extending through said housing, an electrically conductive element extending externally of said housing, a bearing surface internally of said housing and positioned substantially at the center thereof, a rotor positioned substantially at the center of said housing and upon said bearing surface, a wiper arm ai'lixed to said rotor and having slidable engagement with said resistance element, and means electrically interconnecting said wiper arm and said electrically conductive clement to provide external connection to a movable point on said resistance element intermediate said pair of lixed electrical connections, said bearing surface and said electrically conductive element being secured to said housing and forming therewith substantially sealed portions of said enclosing walls, said bearing surface being a cup-shaped member and said rotor being an electrically conductive member to which said wiper arm is electrically connected, said rotor having a projection extending therefrom and into bearing contact with said cupshaped member.

4. A potentiometer in accordance with claim -3 in which said electrically conductiver member extending from said rotor is a sleeve fitted over the lower surface ot said rotor and to which the wiper arm is electrically connected.

5. A potentiometer comprising a housing defining a cavity, a resistance element positioned within said cavity, a plurality of electrical connections to said resistance clement, one of said electrical connections having slidable contact with said resistance element and including a pin member rigidly affixed to, sealed with, and extending through said housing and into said cavity, an electrically non-conductive rotor member having an opening axial therein which is in bearing contact with and disposed about said pin member and having an opening transverse to and communicating with said axial opening, and a wiper arm having first and second portions, said first portion being in sli-fiable contact with said resistance element, said second portion being positioned within said transverse opening and mechanically locked between said pin member and said rotor member.

A potentiometer in accordance with claim 2 in which said bearing surface is a cup-shaped member and said rotor is an electrically conductive member to which said wiper arm is electrically connected, said rotor having a projection extending therefrom .and into bearing contact with said cup-shaped member, and in which said cavity is at least partially illed with an insulative viscous material to mechanically damp vibrations of said wiper arm.

7. A potentiometer comprising a housing defining a cavity, a resistance element positioned within said cavity, a plurality or electrical connections to said resistance element, one of said electrical connections having slidable contact with said resistance element and including a pin member rigidly ai'iixed to, sealed with, and extending through said housing and into said cavity, an electrically non-conductive rotor member having an opening axial therein which is in bearing contact with and disposed about said pin member and having an opening transverse to and communicating with said axial opening, and a wiper arm having tirst and second portions, said irst portion being in slidable Contact with said resistance element, said second portion being positioned within said transverse opening and mechanically locked between said pin member and said rotor member, said second portion oit' said wiper arm having a protrusion therefrom having a thickness substantially the same as the width of said transverse opening, and said protrusion being at least partially seated within said transverse opening to provide mechanical rigidity to said iirst portion of said wiper arm.

3. A potentiometer comprising: a housing including an electrically non-conductive base member having irst, second and third electrically conductive leads spaced apart and extending therethrough, said base having an annular portion extending upwardly therefrom and dcning a ledge intermediate the ends thereof, a resistance element seated upon said ledge, electrical connections between the ends of said resistance element and said rst and second electrical leads, said third electrical lead including a pin member extending upwardly into the interior of said housing, an electrically non-conductive rotor having an axial opening extending at least partially therethrough, said axial opening receiving said pin member to thereby rotatably support said rotor, a slotted opening transverse of said axial opening and communicating therewith, a wiper arm in slidable engagement with said resistance element and extending through said slotted opening, said wiper arm being disposed between said pin and said rotor member to thereby retain said wiper arm in place with respect to said rotor and to provide electrical connection to said resistance element, and a head upon said rotor, said head including a recess adapted to receive an O-ring seal and having means ai'ixed thereto for permitting manual adjustment of said wiper arm upon said resistance element.

9. A miniature potentiometer comprising: a housing including an electrically non-conductive base member having irst, second and third electrically conductive leads spaced apart; and extending therethrough as plug-in connecting pins, said base member having an annular portion extending upwardly therefrom and dening a ledge intermediate the ends thereof, a resistance element seated upon said ledge, electrical connections between the ends of said resistance element and said rst and second electrical leads, said third electrical lead including a pin member extending into the interior of said housing, an electrically non-conductive rotor having an axial opening extending at least partially therethrough, said axial opening receiving said pin member to thereby rotatably support said rotor, a slotted opening transverse of said axial opening and communicating therewith, a wiper arm in slidable engagement with said resistance element and extending through said slotted opening, said wiper arm being disposed between said pin and said rotor member to thereby retain said wiper arm in place with respect to said rotor and to provide electrical connection to said resistance element, and a head upon said rotor, said head including a recess adapted to receive an O-ring seal and an extension protruding from said housing to thereby permit manual adjustment of said wiper arm upon said resistance element, said pin member extending substantially perpendicularly to and approximately midway into said base member from outside said housing at a point oil-center with respect to said housing and base member, said pin member having a right angle bend at said offcenter point from which it extends within said base member to a point approximately on-center with respect to said housing and having a second right angle bend at said on-center point from whence said pin member extends perpendicularly to said base member into the interior of said housing.

lil. A potentiometer comprising: a housing including an electrically non-conductive base member having rst, second and third electrically conductive leads spaced apart and extending therethrough, a resistance element disposed within said housing along an inner preiphery thereof, electrical connections between the ends of said resistance element and said first and second electrical leads, said third electrical lead including a pin member extending upwarly into the interior of said housing, an electrically non-conductive rotor having an axial opening extending at least partially therethrough, said axial opening receiving said pin member to thereby rotatably support said rotor, a slotted opening transverse of said axial opening and communicating therewith, a wiper arm in slidable engagement with said resistance element and extending through said slotted opening, said wiper arm being disposed between said pin member and said rotor member to thereby retain said wiper arm in place with respect to said rotor and to provide electrical connection to said resistance element, and a head upon said rotor, said head including a recess adapted to receive an or-ring seal and a slotted extension protruding from said housing to thereby permit manual adjustment of said wiper arm upon said resistance element.

11. A subminiature, sealed potentiometer comprising: a housing having iirst and second bases and defining, internally, a substantially circularily cylindrical cavity having an axis extending substantially perpendicularly between said bases, a toroidally shaped resistance element disposed within said cavity about the circular periphery thereof, a pair of xed leads connected to said resistance element and extending through said housing, a third ixed lead extending through said housing, a rst bearing surface within said housing and disposed centrally on said tirst base, an annular second bearing surface within said housing disposed on said second base symmetrically about said axis, said rst and second bearing surfaces being axially separated etectively by a predetermined distance, a rotor member disposed substantially within said housing and having bearing surfaces separated by an axial length which is less than said predetermined distance by a predetermined increment such that said axial length plus said increment equals said distance, a resilient, sealing C-ring disposed concentrically about said axis between said second bearing surface of said second base and one of said bearing surfaces of said rotor and having an axial length when appreciably axially compressed equal to said predetermined increment, said second base being bored centrally of said second bearing surface to provide mechanically revolvable communication from externally of said housing to said rotor, a wiper arm disposed on said rotor in engagement with a point movable on the surface of said resistance element when said rotor is rotated, and conductive means within said housing for connecting said wiper arm to said third ixed lead, said housing, said leads, said O-ring, and that portion of the surface of said rotor disposed radially within said second bearing surface forming a sealed cavity.

12. The invention according to claim 8 in which said O-ring is disposed within said housing and in which said rotor includes a body portion disposed within said housing in axially compressive stress between said pin member and said O-ring.

13. The invention according to claim 10 in which said 0-ring is disposed within said housing and in which said rotor includes a body portion disposed within said housing in axially compressive stress between said pin member and said O-ring.

No references cited. RICHARD M. WOOD, Primary Examiner. 

5. A POTENTIOMETER COMPRISING A HOUSING DEFINING A CAVITY, A RESISTANCE ELEMENT POSITIONED WITHIN SAID CAVITY, A PLURALITY OF ELECTRICAL CONNECTION TO SAID RESISTANCE ELEMENT, ONE OF SAID ELECTRICAL CONNECTIONS HAVING SLIDABLE CONTACT WITH SAID RESISTANCE ELEMENT AND INCLUDING A PIN MEMBER RIGIDLY AFFIXED TO, SEALED WITH, AND EXTENDING THROUGH SAID HOUSING AND INTO SAID CAVITY, AN ELECTRICALLY NON-CONDUCTIVE ROTOR MEMBER HAVING AN OPENING AXIAL THEREIN WHICH IS IN BEARING CONTACT WITH AND DISPOSED ABOUT SAID PIN MEMBER AND HAVING AN OPENING TRANSVERSE TO AND COMMUNICATING WITH SAID AXIAL OPENING, AND A WIPER ARM HAVING FIRST AND SECOND PORTIONS, SAID FIRST PORTION BEING IN SLIDABLE CONTACT WITH SAID RESISTANCE ELEMENT, SAID SECOND PORTION BEING POSITIONED WITHIN SAID TRANSVERSE OPENING AND MECHANICALLY LOCKED BETWEEN SAID PIN MEMBER AND SAID ROTOR MEMBER. 